Plasma Generation Under Low Air-pressure And Study Of Its Electrical And Optical Characteristics

Large-volume plasma can be generated under low gas pressure, by using different power source and various coupling methods. This kind of plasma has promising application prospects in areas like material processing, activation and regeneration of catalysts, biomedicine, environmental protection, and so on. Due to low density of media particles and thus longer free path of the electrons, discharge phenomenon under low pressure is so different from that under atmospheric pressure, that uniform plasma of a rather large volume could be more easily generated with a low media temperature and a high electron temperature. The current technologies usually use a MHz or even GHz high frequency power source to inject energy into plasma, through various ways of electrode arrangement. But these generation methods can’t acquire a high density of plasma while the gas pressure stays rather low, and can’t separately control the temperature of the media and of the electron. Additionally, these technologies often require complex and very expensive equipment, thus facing difficulties when scaling up. Limited understanding of the low-pressure discharge process ultimately leads to obstacles, when dealing with the problems encountered in industrial applications.In this paper, uniform plasma of a maximum volume of about20L is generated, using a bipolar pulsed power source and parallel plate electrodes, under pressure of10～100Pa, in a homemade vacuum reactor. Measurement of the time-varied voltage and current of the reactor during discharge has been undertaken, and we obtained the voltage starting a uniform discharge, also the relationship between power and parameters like pressure, electrode distance, electrode area, pulse frequency, etc., under several kinds of medium like air, oxygen, and argon. Information about radical components are also obtained by surveying the emission spectroscopy under different pressure and peak voltage. Moreover, we tried to study the discharge process under repetitive pulsed power input, and tried to detect the growth rate of low-pressure plasma, by using high speed CCD and a homemade PMT device. With all the works done, we provide a more solid experimental basis for the understanding of the low-pressure pulsed discharge phenomenon, and for the design of such type of plasma source.